浆池传热的实验研究

在模拟浆池中,由于传热过程和传质过程的相似,通过对温度场分布的研究,掌握浆池中的传热传质状况。通过对实验结果的分析,得出加强浆池中氧化空气与浆液之间的传热传质的措施有助于提高搅拌速度;布置更多的空气分布喷嘴,使得产生的气泡个数增加而体积减小;适当增加喷嘴的总面积,降低空气鼓出的速度。另外,对于实验中的浆池,提出了一个传热系数的拟合公式。     

Mass transfer from cylindrical pellets submerged in parallel flowing fluid streams

A model is proposed wherein overall mass transfer from single cylinders of benzoic acid placed in parallel flowing water streams depends on different hydrodynamic regimes prevailing along the surfaces of the cylinder. The results for laminar and turbulent conditions are correlated in terms of Sherwood and Reynolds numbers. The mass transfer in the wake region of the cylinder is observed to be significantly different from the boundary layer mass transfer through the lateral surface or the stagnation and boundary layer mass transfer through the leading frontal area.     

Enhancement of mass transfer from particles by local shear-rate and correlations with application to drug dissolution

We analyze hydrodynamic enhancement of mass (or heat) release rate from small spherical particles within fluid flows from local flow shear-rate, with application to drug dissolution. Combining asymptotic theories in the high/low shear Peclet number limits in Stokes flow with 205 carefully-developed computational experiments, we develop accurate correlations for shear enhancement of Sherwood/Nusselt number (Sh/Nu) as a function of shear Peclet and Reynolds number (S^*, Re _S). The data spanned S^* from 0 to 500 and Re _S from 0 to 10. In Stokes flow our correlations are highly accurate over the entire S^* range, whereas for finite Re _S < 1 accuracy is good for S^* up to a few thousand. Shear enhancement results from highly three-dimensional spiraling flow created by particle spin. We develop a model for particle slip velocity that is inserted into the Ranz/Marshall correlation to show that shear-rate enhancement strongly dominates convection, a result important to drug dissolution.     

多级雾化旋转填料床的传质性能

以两级雾化超重力旋转床为例,用化学吸收法考察了超重力因子β、液体流量、气体流量等对体积传质系数kyα的影响。结果表明:多级雾化超重力旋转床的体积传质系数随气液流量的增加而增加,在β较小时,实验曲线的斜率较大,kyα随β的增加急剧增加;但是当β超过100后,曲线的斜率减小,kyα随β的增加缓慢增大。     

Mass transfer from discrete gas bubbles in a reciprocating plate column

Measurements have been made of the uptake of oxygen in water from a series of discrete bubbles released into a 5 cm diameter reciprocating plate column. The rate of increase of dissolved oxygen in the water has provided data on the average mass transfer coefficients under the following conditions; (a) free rise in the absence of plates, (b) bubbles rising through a static plate assembly and (c) bubbles rising through moderately agitated plates (frequency up to 1.28 Hz). It was found that the mass transfer coefficients were higher under condition (b) than (a), and were further increased under condition (c). The results were compared with earlier data on mass transfer to agitated bubble dispersions.     

稀盐酸萃取林可霉素药品中B组分的传质研究

采用双膜理论对酸水萃取正丁醇溶剂中林可霉素B组分的传质过程进行了分析,分析结果表明传质阻力主要集中在滴内。在往复振动筛板萃取塔内,对酸水萃取正丁醇溶剂中林可霉素B组分进行了实验研究,考察了输入能量和通量对总传质系数的影响。研究表明:虽然输入能量可以强化滴外传质,但对总传质系数的影响却较小;而通量的增加使不同液滴间的碰撞、聚合、再分散作用加强,从而强化了液滴内传质,因此通量对总传质系数的影响比较大。所以,对于酸水萃取正丁醇溶剂中林可霉素B组分这类传质阻力主要集中在滴内的物系,在设计往复振动筛板萃取塔时不应将提高输入能量作为强化传质的主要控制手段,而是提高通量。     

沼气提纯过程中醇胺溶液吸收CO2传质性能

醇胺溶液吸收CO₂是沼气提纯领域重要的研究课题。在实验填料吸收塔中,以乙醇胺(MEA)、二乙醇胺(DEA)为吸收剂,研究了吸收剂浓度、进气流量、CO₂浓度、进液温度对吸收过程转化率η、吸收速率N以及气相总体积传质系数K_Ga_e的影响。结果表明,吸收剂浓度增加可有效提高η、N及K_Ga_e;进气流率增加,η逐渐降低,N先增加后降低,K_Ga_e先增加后降低最终趋于稳定;随着CO₂浓度增加,η和K_Ga_e不断降低,N逐渐增加;随着进液温度升高,η和K_Ga_e均先升高后降低;MEA、DEA的最佳进液温度在40～60℃之间,并随CO₂负载量增大而逐渐降低。研究结果对于醇胺溶液吸收法沼气提纯技术的研究开发和实际应用有参考作用。     

气升式环流反应器强制振荡周期对传质影响的研究

在同一反应器中比较了不同振荡周期下的气液传质特性,为最优强制振荡周期的确定提供了实验依据和分析基础。选择体积传质系数及气含率作为传质研究的主要评价指标,实验结果表明,动态操作下的传质效果明显优于稳态,而不同振荡周期传质效果也大不一样。在0.8~2.4m3h-1的气速范围内,由静压力、导流管顶部截面流体速度、全床气含率(及传质系数)周期性变化所确定的振荡周期TP、TV、TK比稳态操作下的全床平均传质系数分别提高了3.92%~27.3%,2.35%~24.5%,28.2%~43.3%。由反应器内全床平均气含率或传质系数确定的振荡周期TK是最佳振荡周期。     

乙酸仲丁酯-乙酸-水萃取体系的传质行为

为了更好地了解乙酸仲丁酯-乙酸-水萃取体系的传质规律,对该体系的传质行为进行了研究.首先,采用投影光学法实验观测了体系的Marangoni对流现象,实验发现当水相中乙酸浓度≥4.33 mol· L-1时,该体系的传质过程出现了Marangoni对流.其次,用单液滴法考察了液滴大小、连续相浓度、温度等因素对该体系自由运动...     

Chain transfer in vinyl chloride polymerization in the presence of polybutadiene

Vinyl chloride (M) was polymerized in the presence of a low molecular weight polybutadiene (S) at 60°C in the presence of x,x′-azobisdiisobutyronitrile as initiator, which does not affect the transfer reaction. The raw material was fractionated for the purpose of separating the pure PVC homopolymer. The number-average molecular weight of PVC homopolymer, determined by size exclusion chromatography (SEC), was used in Mayo's equation to obtain the value of the transfer constant Cs, which was found to be 11. A simplified reaction scheme is given according to which it is possible to explain why the reaction yield decreases and the crosslinking density increases by increasing the [S]/[M] ratio.     

Mass transfer coefficient of tubular ultrafiltration membranes under high‐flux conditions

The effect of suction flow on the mass transfer coefficient of tubular ultrafiltration membranes, in particular that under a high‐flux condition, was studied. We pointed out that is proportional to under turbulent conditions, and that the proportional constant, b, exceeds 0.023 when the effect of suction flow is not negligible. We conducted the velocity variation method using ultrafiltration membranes with MWCOs of 20k and 100k and dextrans having molecular weights of 40,000 and 70,000 at the conditions, where exceeded . We demonstrated that the effect of suction flow includes not only flux but also the diffusion coefficient of solute, and that the ratio of the flux to the diffusion coefficient, expressed as , is an important index. Finally, we concluded that , when is smaller than , giving the Deissler equation itself, and that , when exceeds . © 2017 American Institute of Chemical Engineers AIChE J, 64: 1778–1782, 2018     

静止非牛顿流体中气泡生成过程的传质

气泡生成过程中气液传质是气液接触设备的设计、优化的重要参考指标。以二氧化碳气泡在羧甲基纤维素钠(carboxymethyl cellulose,CMC)溶液中生成过程中的传质为研究对象,分别考察了气速、CMC溶液浓度、针头直径对气泡生成过程气液传质的影响,采用具有CCD显微相机的动态接触角分析仪测量了气泡形状、表面积和体积的变化,进而获得气泡生成过程气液传质系数k_l。实验结果表明,CMC浓度从0.2%增加到0.8%,黏度逐渐增大,传质系数随CMC浓度的增大而增大;针头直径从2.5 mm增加到4 mm,传质系数也随之增大;气速从1 ml·min^-1增加到9 ml·min^-1,传质系数也逐渐增大。     

水冷却塔传质系数计算模型初探

冷却塔填料表面传热传质过程的理论计算都与一个经验参数——传质系数有关。因为过去人们都将这个参数表示成水气流量的函数,未能正确地反映传质系数对水冷却塔传热传质过程重要影响的本质。采用液膜蒸发理论,将传质系数表示成湿空气温差及压差的函数,新的计算方法将改善冷却塔的设计计算。     

Mass transfer modeling during cross-flow filtration of non-newtonian fluids

The film theory was used to determine the mass transfer coefficient for the cross-flow filtration of guar gum solutions. We investigated their variation with cross-flow velocity and concentration. Comparing the experimental results with the Sherwood correlation generalized for power law fluids and with two models found in the literature led to the evaluation of an effective diffusion coefficient for each model. This parameter was shown to depend on cross-flow velocity and concentration.     

氯化钠存在下微波辐射高稠原油脱水研究

采用SH9402微波反应系统对含水质量分数50%的大庆稠油进行了微波辐射脱水研究。考察了微波辐射时间、压力、功率以及氯化钠对原油脱水率的影响。在微波辐射时间4 min,压力0.2MPa,功率350 W,氯化钠质量分数为3%的条件下,脱水率达到了96.67%。该方法改善了工艺条件,拓宽了微波辐射原油脱水的应用范围。     

降膜微反应器中CO_2化学吸收过程传质行为

Gas phase mass transfer in falling film microreactors (FFMRs) with the absorption of CO₂ into aqueous solutions of NaOH was investigated. The overall gas-phase mass transfer coefficient increases with NaOH concentration, but decreases as the concentration of CO₂ increases. There exists an entrance effect, hindering the mass transfer, which is caused by the dead volume for gas-phase flow in the gas chamber in FFMRs. The entrance effect has a larger impact in a shorter FFMR owing to the relatively large dead volume with respect to that of gas chamber. A decrease in the depth of gas chamber facilitates the mass transfer process. Therefore, the gas-phase entrance or geometry of the gas chamber should be designed appropriately to reduce the entrance effect and improve the mass transfer.     

动力波洗涤器中碱液吸收低浓CO_2的传质特性

为研究动力波洗涤器内的气液传质特性,在动力波洗涤器中,进行NaOH溶液吸收混合气体中微量CO2气体的吸收实验。参考填料塔中钠碱溶液吸收低浓气体的传质模型,测定了动力波洗涤器中NaOH溶液吸收低浓CO2的气相体积总传质系数KGa及吸收效率η。研究了气相速度、NaOH溶液质量分数及液气比对KGa的影响,结果表明:KGa随着气相速度及NaOH溶液质量分数的增加而增大,但NaOH溶液质量分数小于气相速度对KGa的影响;随着液气比的提高,KGa逐渐减小,η开始随着液气比的提高而增加,但到一定数值后,效果不明显;回归了KGa的准数关联式,并依据液气比对KGa及η的综合评价,提出洗涤管直径为100 mm,NaOH溶液质量分数为10%,液气比操作范围在0.005—0.025时,动力波洗涤器具有较高的综合传质性能,为工业应用提供参考。     

Effects of 1,4-naphthoquinone on aluminum corrosion in 0.50 M sodium chloride solutions

Effects of 1,4-naphthoquinone (NQ) have been investigated as a corrosion inhibitor for aluminum in aerated and de-aerated solutions of 0.50 M NaCl using potentiodynamic polarization, chronoamperometry (CA), open-circuit potential (OCP), electrochemical impedance spectroscopic (EIS), scanning electron microscopic (SEM), cyclic voltammetric, and quartz crystal analyzer (QCA) techniques. These measurements revealed that the presence of NQ shifted the corrosion and pitting potentials to more noble values and decreased the anodic currents in the passive region in both aerated and de-aerated chloride solutions, and the surface and polarization resistances are increased as the concentration of NQ is increased. The most effective concentration of NQ for corrosion inhibition was found to be 1.0 × 10⁻³ M in both aerated and de-aerated chloride solutions. The QCA data indicate that adsorption of NQ molecules plays an important role in protecting the pits on the aluminum surface. The SEM images show that the presence of NQ decreased the severity of the pitting corrosion of aluminum to a great extent at −675 mV versus Ag/AgCl.     

2-乙基-1，3-己二醇萃取硼酸的传质系数

单液滴法因其测量结果精确与实验设备简单等优点广泛应用于萃取过程中的传质研究。应用此方法研究了硼酸在2-乙基-1,3-己二醇-甲苯/卤水体系中的传质系数。结果表明：传质系数随着有机相2-乙基-1,3-己二醇浓度、卤水相硼酸浓度及温度的增加而增大。通过双膜传质理论分析,并引入修正的传质系数关联式,将双膜传质模型应用到此萃取体系中,建立了新的针对此体系的传质系数模型。新模型的计算值与实验值的平均相对误差为7.59 %,两者吻合良好,因此,该模型可用于2-乙基-1,3-己二醇-甲苯体系萃取硼酸过程的设计与放大。